Deepwater Challenges Pipeline Installation Case Seminar Nasional Oceano, ITS, 28 March 2011, Surabaya Gunawan Suwarno, 28 March 2011 DeepLay Energy Services email : marketing@deep-lay.com 1
Deepwater Development 2
Deepwater Challenges ( For Subsea Pipeline ) Design Design ( Issues on Lateral Buckling or Pipeline Walking, for HPHT Pipeline ) Seabed ( Issues on Freespan, Seabed Intervention, Seabed Movement ) Installation Installation ( Issues on Lay Tension Requirement ) Installation Risks Management ( typically issued flooded Pipe ) 3
Pipeline Installation Method ( Slay and Jlay ) SLay JLay 4
Pipeline Installation Method ( Slay and Jlay ) Stinger Tip End Angle JLay Tower Angle For the same angle, by Considering Equilibrium, the H on Slay will be much larger than Jlay because of Stinger Contact Forces Tension can be reduced When Angles are closed to 90 Degrees 5
Deepwater Challenges ( Installation ) Typically the main issues is the lay tension requirement, deep water will require bigger tension ( on Slay and or Jlay ) because the length of catenary line. The length of catenary line can be reduce by having almost vertical lay angle ( while on Slay, the selection of the angle is depending on the stinger radius ) Selection of Stinger Radius is depending on allowable Stress / Strain during Installation 6
Pipeline Installation Limits Traditional Code Static : 0.72 SMYS ( Dnv Stress DnV1981 ) Dynamic : 0.96 SMSY ( DnV Stress DnV1981 ) Or DnV OSF101 Simplified Criteria 7
Relation Between Stress and Strain ( X65 ) Stress, Strain Elastic % to Yield (Mpa) ( ) (%) 436.3 0.97 0.350 430.2 0.96 0.305 418.5 0.93 0.250 394.0 0.88 0.200 310.7 0.69 0.150 8
Local Buckling Checks, DnV OS F101 Stinger DCC, Sagbend & Last Roller LCC Issues - Criteria for DCC and LCC, typically DCC is Stinger Fixed, Ramp ( Controlled Area ) and LCC is at Stinger Last Roller, Floating Stinger System and Sagbend 9
Pipeline Installation Limit, Local Buckling Check For Steep Slay For Deep Water Slay Application At OverBend Section / Stinger, used Displacement Controlled Condition ( Similar to Reeling ) At Stinger Tip, used Load Controlled Condition Avoid Contact or High Load on Stinger Tip Stinger curvature / radius will be based on DCC which will give a high allowable strain limits ( It could go above 0.5% ) > Smaller Radius ( But Beware of Residual Strain ), Near Vertical Stinger Angle > Less tension Requirement 10
Pipeline Installation Limits The New Pipeline Code allows us to use a smaller stinger radius which will give a possibly to lay pipeline on a deeper water depth. But Smaller radius will create a high strain during installation which will effect the residual strain post installation. ( some case will create pipe rotation, It will become an issued on pipeline with In Line Structures ) The residual strain will effect the residual Pipeline Ovality and Pipe Ovality will reduce the maximum Pipe Collapse Capacity Pipeline on Deepwater. And High Strain/Stress level will also have impact on maximum fatigue standby time during installation. 11
Pipelaying And Vessel Position 12
Pipelaying And Vessel Position Layback Deep water lay vessel is usually powered by DP( Dynamic Positioning, positioning based on thrusters and reference system ) * Not limited to water depth * More control on positioning * Mooring/anchor handling spreads not required 13
Deepwater Challenges For Pipelaying, the Thruster Force is used to positioning the vessel against the catenary Horizontal Load 14
Typical Examples of DP Station keeping Limiting Conditions at most unfavourable wind directions Case Pipelay Wind Wind Wave Wave Current Thruster Tension Speed Direction Hs Tz Speed Off ( Te ) ( Knot ) ( Deg ) ( m ) ( Sec ) ( Knot ) ( ) 1 150.0 32.80 90.00 3.30 6.00 1.00 None 15
Slay Pipeline Installation Loads The Tension capacity reflect the lay capabilities Lay tension DP Thrust / Bottom tension DP Thrust capacities show DP Station Keeping Capabilities during Pipelay DP Thrust / Bottom tension 16
DeepWater Slay Load Check Load cheks During Pipelay Analyses ( DP vessel ) Maximum Dynamic Top Tension is below the maximum allowable Tensioner Capacity Maximum Horizontal Tension ( Bottom Tension ) is below the allowable DP Thrust Station Keeping Capacity with Sufficient weather Windows and emergency case of one of Thrust Failures. What If the un planned flooded pipe happen due to wet Buckle? 17
Deepwater Installation Risks, Flooded Pipeline The biggest Risks for Pipeline Installation in Deepwater is unplanned flooded pipe due to pipe buckle. This incident will increase the lay tension significantly ( specially for big Diameter of Pipeline ). Typically, Contractor do not design the pipelaying vessel to be able to lay safely the flooded pipe but Contractor Pipelaying Vessel must be able to safely abandon the flooded pipe without free fall or damaging the main component of lay system ( stingers or Jlay Tower ). For JLay, typically the collar need to be able to hold the flooded pipe. 18
In case of Flooded Lay Tension increased significantly. The Lay Tension may be above the Tensioner capacity If Lay tension above the capacity, the Tensioner will be on breakmode, if beyond brekamode pipe will drop (freefall) Bottom tension will increase in line with pipe lay Tension If Bottom tension above the DP Station Keeping Capabilities, the vessel will not be able to keep in Position ( move Backward ), Until equilibrium 19
Flooded Case Load Check ( Slay ) Load checks During Wet Buckles Case ( DP vessel ) Maximum Top Tension is below the maximum allowable Tensioner Break Capacity capacity Most likely, at Wet Buckle condition, the vessel will not able to hold the catenary ( above the station keeping capabilities), So the vessel will move backward until reaching the equilibrium position ( Horizontal Tension equal <= Capacity of DP Forces ) At the above condition the Winch should capable to laydown the pipe safely on the seabed ( Winch Tension Capacity is above the lay tension at drift position ) The Stinger Structural should be verified against this loadings 20
Sample Cases of Flooded Case Study Pipelay Vessel Configuration No of Tensioner : 3, with Total Capacity : 300Te Max Lay Down Winch Capacity : 360 Te 21
Sample Cases of Flooded Case Study No of Tensioner : 3 Max Lay Tension : 3 * 100te = 300 Te Max breakmode Tension : 3 * 217te = 661 Te 22
Samples Case of Flooded Case Study Stinger Profile 23
Sample Cases of Flooded Case Study Static Dry at 1000m water Depth The required Tension is below the max Tensioner Capacity OK 24
Sample Cases of Flooded Case Study Static Wet Buckle at maximum DP Thrust The required Tension is below the max Tensioner Break Capacity OK 25
Sample Cases of Flooded Case Study Static Wet Buckle at Low DP Thrust for abandonment The required Tension is below Winch Capacity OK 26
Flooded Case Load Check ( Slay ) Beside the above, There is also Stinger Integrity Check, to make sure that Stinger and its connection does not failed structurally under the above accidental load. 27
Deepwater Challenges Terima Kasih 28